As the world's population expands and its economy increases, the atmospheric concentrations of carbon dioxide are warming the earth causing climate change. However, the global energy system is moving steadily away from the carbon-rich fuels whose combustion produces the harmful gas. Experts say atmospheric levels of carbon dioxide may be double that of the pre-industrial era by the end of the next century, but they also say the levels would be much higher except for a trend toward lower-carbon fuels that has been going on for more than 100 years. Furthermore, fossil fuels cause pollution and are a causative factor in the strategic military struggles between nations.
For nearly a century and a half, fuels with high amounts of carbon have progressively been replaced by those containing smaller and smaller amounts of carbon. First wood, which is high in carbon, was eclipsed in the late 19th century by coal, which contains less carbon. Then oil, with a lower carbon content still, dethroned “King Coal” in the 1960's. Now analysts say that natural gas, lighter still in carbon, may be entering its heyday, and that the day of hydrogen—providing a fuel with no carbon at all—may at last be about to dawn. As a result, experts estimate the world's economy today burns less than two-thirds as much carbon per unit of energy produced as it did in 1860.
In the United States, it is estimated, that the trend toward lower-carbon fuels combined with greater energy efficiency has, since 1950, reduced by about half the amount of carbon spewed out for each unit of economic production. Thus, the decarbonization of the energy system is the single most important fact to emerge from the last 20 years of analysis of the system. It had been predicted that this evolution will produce a carbon-free energy system by the end of the 21st century. The present invention shortens that period to a matter of years. In the near term, hydrogen will be used in fuel cells for cars, trucks and industrial plants, just as it already provides power for orbiting spacecraft. But ultimately, hydrogen will also provide a general carbon-free fuel to cover all fuel needs.
As noted in recent newspaper articles, large industries, especially in America, have long been suspicious of claims that the globe is warming and have vociferously negated the science of climate change. Electric utilities have even tried to stoke fears among ordinary folk that international treaties on climate change would cut economic growth and cost jobs. Therefore, it is very encouraging that some of the world's biggest companies, such as Royal Dutch/Shell and BP Amoco, two large European oil firms, now state plainly what was once considered heresy: global warming is real and merits immediate action. A number of American utilities vow to find ways to reduce the harm done to the atmosphere by their power plants. DuPont, the world's biggest chemicals firm, even declared that it would voluntarily reduce its emissions of greenhouse gases to 35% of their level in 1990 within a decade. The automotive industry, which is a substantial contributor to emissions of greenhouse gases and other pollutants (despite its vehicular specific reductions in emissions), has now realized that change is necessary as evidenced by their electric and hybrid vehicles.
Hydrogen is the “ultimate fuel.” In fact, it is considered by most to be “THE” fuel for the next millennium, and, it is inexhaustible. Hydrogen is the most plentiful element in the universe (over 95%) and was the first element created by the “Big-Bang.” Hydrogen can provide an inexhaustible, clean source of energy for our planet which can be produced by various processes which split water into hydrogen and oxygen. The hydrogen can be stored and transported in solid state form. The hydrogen can also be readily generated and stored. For example, economical, lightweight, triple-junction amorphous silicon solar cells (an invention pioneered by Stanford R. Ovshinsky, one of the instant inventors) such as those set forth in U.S. Pat. No. 4,678,679, (the disclosure of which is herein incorporated by reference) can be readily disposed adjacent a body of water, where their inherently high open circuit voltage can be used to dissociate water into its constituent gases, and collect the hydrogen so produced. Also, by placing these high efficiency solar panels on nearby farms, in water, or on land. Electricity can be generated to transport and pump the hydrogen into metal hydride storage beds. The hydrogen storage capacity of the hydrogen storage alloys allow hydrogen to be stored in solid form for transport by barge, tanker, train or truck in safe, economical form for ultimate use. Energy is the basic necessity of life and civilization for any society today and the use of hydrogen in the manner described herein as the basic source of energy would end wars fought for control of fossil fuels. Instead of “from well to wheel,” the phrase now recited will be “from source to wheel.”
In the past considerable attention has been given to the use of hydrogen as a fuel or fuel supplement. While the world's oil reserves are depletable, the supply of hydrogen remains virtually unlimited. Hydrogen can be produced from coal, natural gas and other hydrocarbons, or formed by the electrolysis of water, preferably via energy from the sun which is composed mainly of hydrogen and can itself be thought of as a giant hydrogen “furnace”. Moreover hydrogen can be produced without the use of fossil fuels, such as by the electrolysis of water using nuclear or solar energy, or any other form of economical energy (e.g. wind, waves, geothermal, etc.). Furthermore, hydrogen, although presently more expensive than petroleum, is an inherently low cost fuel. Hydrogen has the highest density of energy per unit weight of any chemical fuel and is essentially non-polluting since the main by-product of “burning” hydrogen is water. Thus, hydrogen can be a means of solving many of the world's energy related problems, such as climate change, pollution, strategic dependancy on oil, etc., as well as providing a means of helping developing nations.
While hydrogen has wide potential application as a fuel, a major drawback in its utilization, especially in mobile uses such as the powering of vehicles, has been the lack of acceptable lightweight conmpact hydrogen storage medium. Conventionally, hydrogen has been stored in pressure-resistant vessels under a high pressure or stored as a cryogenic liquid, being cooled to an extremely low temperature. Storage of hydrogen as a compressed gas or liquid involves the use of large and/or cryogenic vessels, making the use of hydrogen to power vehicles less feasible.
Alternatively, certain metals and alloys have been known to permit reversible storage and release of hydrogen. In this regard, they have been considered as a superior hydrogen-storage material, due to their high hydrogen-storage efficiency. Storage of hydrogen as a solid hydride can provide a greater volumetric storage density than storage as a compressed gas or a liquid form. Also, hydrogen storage in a solid hydride presents fewer safety problems than those caused by hydrogen stored in containers as a gas or a liquid. These alloys are fully described in U.S. Pat. No. 6,193,919, entitled “High Storage Capacity Alloys Enabling a Hydrogen-based Ecosystem”, which is hereby incorporated by reference.
With these developments in the storage of hydrogen, hydrogen now has a viable use as a fuel to power vehicles. Solid-phase metal or alloy system can store large amounts of hydrogen by absorbing hydrogen with a high density and by forming a metal hydride under a specific temperature/pressure or electrochemical conditions, and hydrogen can be readily released by applying heat.
With hydrogen now being a viable source to power vehicles, considerable research has been performed on designing internal combustion engines to run on hydrogen rather than fossil fuels. In these designs, a hydrogen/air mixture is combusted inside an internal combustion engine much like gasoline and other hydrocarbon fuels are combusted in present day internal combustion engines. With hydrogen, however, catalytic converters are not needed to treat the exhaust to comply with emission standards. Hydrogen burns clean with the only byproduct being water.
Considerable research has also been performed on using fuel cells to power vehicles. Fuel cells, like batteries, operate by utilizing electrochemical reactions. Unlike a battery, in which chemical energy is stored within the cell, fuel cells generally are supplied with reactants from outside the cell to produce an electrical current used to power a vehicle. In fuel cells, a hydrogen stream, an oxygen stream, and an electrolyte stream are used to provide an electric current. Fuel cells offer a number of important advantages over internal combustion engine or generator systems. These include relatively high efficiency, environmentally clean operation, high reliability, few moving parts, and quiet operation. Fuel cells potentially are more efficient than other conventional power sources based upon the Carnot cycle.
For hydrogen to become a viable alternative to hydrocarbon fuels, various systems are needed for the storage and maintenance of hydrogen in vehicles. These systems must allow for simple and efficient refueling to gain acceptance by the general public. The stored hydrogen must also be available from the hydrogen storage system on demand to power a vehicle regardless of the outside temperature during startup or operation.
The present invention describes an innovative design for a heat transfer system used to cool a vehicle's hydrogen storage bed during charging and heat the hydrogen storage bed during operation of the vehicle and startup. The heat transfer system removes heat of hydride formation from the vehicles hydrogen storage vessel to minimize the time needed for refueling the vehicle and supplies heat to the hydrogen storage vessel to aid in the release of hydrogen from the hydrided hydrogen storage alloy during operation of the vehicle and startup.